1. Field of the Invention
This invention relates to an improved scheme for selectively addressing elements comprising a ferroelectric matrix arrangement, such as, but not limited to an information display memory.
2. Prior Art
A conventional method utilized to addess a ferroelectric matrix arrangement, such as that which forms a display memory comprised of x and y orthogonally disposed intersecting lines, is a one-half selection scheme. One example of a ferroelectric matrix arrangement, the ferroelectric elements of which are addressed by the prior art one-half selection scheme is found in U.S. Pat. No. 3,725,899 issued Apr. 3, 1973. To selectively enable a particular element in a matrix of elements to accept information (i.e. charge) supplied via an x-line, the intersecting y-line is addressed with a signal having full reference amplitude. To preserve the prior condition of all other elements of the memory, the associated intersecting y-lines are addressed with a signal having an amplitude corresponding to 1/2 the reference level of full amplitude. Because of the electrical properties of a ferroelectric material, the 1/2 reference signal level utilized in the conventional one-half selection scheme undesirably causes a relatively high depoling of the material from the normally poled remanant state. The poled state is diminished further with repeated 1/2 reference signal pulses which occur during the process of addressing all the elements in the matrix. This repetitive depoling action is known as hysteresis creep to those skilled in the art.
Hysteresis creep adversely reduces the magnitude of polarization that is required to suitably distinguish between an "ON" and "OFF" element. Consequently, information stored by unselected elements can be altered or erased. That is, a large reduction in polarization can cause an unselected element that was driven to an ON condition to have the voltage characteristics of an element of display which is driven to zero polarization. Moreover, when the conventional one-half address selection scheme is employed, the resulting hysteresis creep prevents the use of ferroelectric materials in any memory array applications, inasmuch as the information contained by a ferroelectric memory element may be undesirably changed.